Can Windows and Mac connect to the same LAN Server?

Solution 1:

OS will not halt any way to connect via LAN. Computers with the Java edition of Minecraft can connect to each other. Devices with the Bedrock/Windows 10/Pocket Edition of Minecraft can connect to each other. However, Bedrock and Java editions are different, and therefore incompatible.

Solution 2:

Yes, the type of OS that you have should not determine the type of server you will be able to join, as long as both games are useable on their respective OS.

Some things that could come into play though, considering it is on LAN, are firewalls, and other 'blocking/monitoring' software on either computer.

Here is a reddit thread about some suggestions and tips, and here is a previous Gaming Exchange question and answers. Hope it helps!